不同施肥模式下稻田土壤微生物生物量磷对土壤有机碳和磷素变化的响应

通过15年的红壤稻田长期定位试验,研究了不同施肥模式下土壤微生物生物量磷(MB-P)对土壤有机碳和磷素变化的响应.结果表明红壤稻田有机碳源的长期投入和土壤有机碳的逐年升高使土壤微生物生物量碳(MB-C)维持在较高水平(＞800 mg·kg-1),是稻田土壤MB-P(＞16.0 mg·kg-1)提高的主要原因.长期不施磷肥条件下,土壤全磷含量与试验前相比显著降低(P＜0.05),而土壤有机磷含量平均提高了29.3%;土壤亏损的磷形态主要是无机磷(Al-P、Fe-P、Ca-P和O-P),其中Al-P含量处于最低水平(平均0.5 mg·kg-1).另外,长期不施磷肥土壤的MB-P远高于Olsen法提取态磷(Olsen-P)(＜7.0 mg·kg-1),而稻田土壤MB-P与Al-P呈显著相关(P＜0.05),表明土壤微生物对稻田土壤Al-P、Fe-P、Ca-P和O-P的利用是促进其向有效磷方向转化的关键途径.磷肥配合有机养分循环利用不仅提高了土壤磷库的积累,而且通过土壤微生物的活化有效地提高了土壤磷的有效性.

Responses of microbial biomass P to the changes of organic C and P in paddy soils under different fertilization systems

Based on a fifteen years field experiment in double rice-cropping region of subtropical China, the responses of microbial biomass P (MB-P) to organic C and P in red paddy soils under different fertilization systems were investigated. The results indicated that a long-term input of organic carbon sources and the increasing soil organic carbon made soil microbial biomass remain at a high level (MB-C > 800 mg x kg(-1)), being a main reason of the increase of MB-P. Under long-term zero chemical P fertilization, there was a significant decrease in soil total P (P < 0.05), but soil organic P increased by 29.3% on average. The inorganic P forms in deficit were mainly Al-P, Fe-P, Ca-P and O-P, with the lowest content of Al-P (only 0.5 mg x kg(-1) on average). The content of soil MB-P under zero chemical P fertilization was much higher than that of Olsen-P. Correlation analysis showed that there was a significant relationship (P < 0.05) between MB-P and Al-P, from which, it was deduced that the utilization of Al-P, Fe-P, Ca-P and O-P by soil microbes could be the key approach of promoting these P forms transformed into available P. Chemical P fertilization combined with organic nutrient recycling could not only enlarge the soil P pool, but also improve the P availability.